Synthetic biology and nanotechnology are emerging fields that are revolutionizing the materials, energy, devices, and organisms used in all facets of life. Synthetic biology is an engineering discipline for programming biological systems to achieve new functionalities. Nanotechnology takes advantage of the emergent properties of materials as their characteristic dimensions approach the nanometer scale.
Many of the systems designed for interfacing biological and non-biological materials have used filamentous-phage-displayed peptides which bind to inorganic materials. These methods have found important applications, including ordering quantum dots, creating magnetic and semiconducting nanowires, and building electrodes for lithium ion batteries. However, there are several major limitations with the phage-display approach. Filamentous phages can only accommodate short peptides for surface expression, which can significantly limit the extent to which they can be functionalized. Anisotropic patterning along the length of a phage is difficult to achieve since phage coat subunits to which peptides are fused are randomly incorporated into the phage coat structure. Phage-based nanowires are restricted by the inherent dimensions of the phage itself and cannot be easily extended, shortened, widened, or polymerized. Moreover, since phages are not autonomous living organisms, they are incapable of interfacing inorganic materials with synthetic gene circuits within living cells. DNA has also been used as a template for assembling inorganic materials but DNA is unstable at high temperatures and pH levels which may be necessary for metallization processes (Scheibel et al., (2003) Proc Natl Acad Sci USA 100:4527). In addition, DNA is not readily exported or displayed extracellularly and so, its ability to link living cells with non-living materials is greatly limited.